Have you tried:
- deactivating ALL plugins temporarily to see if this resolves the problem. If this works, re-activate them individually (one-by-one) to find the problematic plugin(s). If you can't get into your admin dashboard, try deactivating via FTP or SFTP or whatever file management application your host provides. If applicible, also remember to deactivate any plugins in the mu-plugins folder. The easiest way is to rename that folder to mu-plugins-old.
- To rule out any theme-specific issue, try switching to the unedited default theme for a moment using the WP dashboard. If you don't have access to your admin area, you can switch to the default theme by renaming your current theme's folder in wp-content/themes and adding "-old" to the end of the folder name using via FTP or SFTP or whatever file management application your host provides. Alternately, you can remove other themes except the default theme. That will force your site to use it.
- resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems (because the hooks remain unless plugins completely removed or some plugins stick around in cached files. So by renaming the folder, you break them and force them inactive).
- If the above troubleshooting steps fail to resolve the issue, try manually re-uploading all files and folders EXCEPT the wp-config.php file and the /wp-content/ directory from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones. Read the Manual Update directions first!
- Always backup everything (including your database) before doing any actions, just in case.

If after renaming the entire plugins folder (wp-content/plugins) and your specific theme folder (wp-content/themes/your-theme-folder) and the default theme still does not work then it is narrowed down to an installation issue. Just be sure you rename YOUR theme folder not the 'themes' folder.

If that doesn't work you should backup all of your files as her post suggests and re-upload all of the WordPress core files and it might very well fix your issue. If that doesn't do it then it could be something in .htaccess or wp-config :)

Deactivating plugins and themes is a trouble-shooting procedure, and refreshing WordPress is not a guarantee since there could be a database problem. Do you have any idea what might have caused this problem to begin? Had you made any changes anywhere just before it happened?

I dont think i can delete the wordpress folders, since on my website it has a lot of "pages" which will get overridden i think. I'll try make a downlaod of everything and then at least i have a backup i can reupload over everything if it doesnt solve the problems.

Should i maybe contact the webhost, could this be a website provider problem?

I dont think i can delete the wordpress folders, since on my website it has a lot of "pages" which will get overridden i think.

Your pages, posts, comments and such are stored in your database, not in WordPress folders, but you definitely do not want to delete your wp-content folder where your theme and uploads are located. To know what to delete and what to not delete, carefully consider this:
"delete all *WordPress* folders and files other than wp-content and wp-config.php"

For example, htaccess is not a *WordPress* file, and you might have other folders and files also that are not WordPress. Leave those alone unless you have some specific reason for doing something with them.

I'll try make a download of everything and then at least i have a backup i can reupload over everything if it doesnt solve the problems.

You will not need to download backups of wp-admin or wp-includes or any of the loose WordPress files other than wp-config.php.

Should i maybe contact the webhost, could this be a website provider problem?

Posts at that other thread seem to indicate refreshing WordPress might solve your problem, but it never hurts to at least as a host whether anything other than WordPress might seem to be broken.